The process through which the basic principles and concepts of computer programming language are acquired by children was investigated via the development and testing of a teaching unit for fourth and sixth grade students. This unit had three components: (1) basic programming without variables; (2) basic programming with variables; and (3) integration of concepts and simple programs into a combined project and presentation of the principles of top-down design. Two studies were undertaken, one in a laboratory setting and the second in a classroom setting. The high variability of achievement by the students was tested and found to be explained by grade level (age) and academic achievement, not gender. It was also found that the data supported the contention that basic computer programming can be introduced at the upper elementary level, but that the introduction of more abstract concepts may need to be postponed to a later stage of learning. Additionally, it is noted that the teaching of structured programming may not necessarily be relevant to the teaching of introductory programming to children. A 25-item bibliography is provided. (EW)